Ringing control system for telephone-exchanges.



for:

" AWE/r Patented Jan. 1, 1918.

. 9 was S. B. WiLHAMS, JR

APPLICATION mu) DEC. 28. 1915.

new

RINGING CONTROL SYSTEM FOR TELEPHONE EXCHANGES..

UNITED STATES PATENT @FFTCE.

SAMUEL E. WILLIAMS, 33., OF BROOKLYN, NEW YORK, ASSIGNOR TO WESTERNELEG- TRIC COMPANY. INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OFNEW YORK.

RINGING CONTROL SYSTEM FOR TELEPHONE-EXCHANGES:

moron-a.

Specification of Letters Patent.

Patented Jan. 11, 1918..

Application filed December 28, 1915. Serial No. 69,066.

T 0 all whom it may concern:

Be it known that I, SAMUEL B. 'Wliiunzvts, J12, a citizen of the UnitedStates, residing at Brooklyn, in the county of Kings and State of NewYork, have invented certain new and useful Improvements in RingingControl Systems for Telephone-EXchanges, of which the following is afull, clear, concise. and exact description.

This inventioii relates to a ringing control system for telephoneexchanges. and is ringing current that is automatically ap plied inestablishing connection with a'line, to ring a particular station otthat line, and to ascertain the sort oi? ringing current a particularconnecting circuit is set to apply.

The system of this invention is such that the setting of the operatorsswitching apparatus to predetermine the character of ringing currentthat to be applied automatically by a particular connecting circuit,brings about certain changes in said circuit which not only areinstrumental in controlling the charactcr of the signaling current thatthis circuit is thus adapted to apply, but also control the display or acorresponding one of a number of signals associated with the operatorsswitching apparatus to indicate to the operator, when she listens in onthis connecting circuit. the sort of ringing current for which theconnecting circuit is set. The organization ot'the. system is such thatwhen a connecting circuit is changed through the agency ot theoperator's switching mechanism to adapt it for the application of acertain sort of ringing current, it remains set to apply'this sort ofcurrent until the connection is taken down or until the operatormanipulates her switching mechanism to change the setting while switchof the eflccted through the agency of an automatic sequence switch type,this switch being arranged to establish the different ringing currentcombinations in different positions of its movement, and being arrangedto move to any predetermined one of its ringing positions under thecontrol of the individual connecting circuit controlling mechanism setby the switching apparatus common to the position.

The above mentioned and other features of the invention will bedescribed in detail in connection with the accompanying drawing. whichillustrates one of the forms in which the invention may be practised. v

In the particular embodiment illustrated, the invention is shown appliedto a connccting circuit terminating in a plug 11, the plug being adaptedto be inserted in a spring jack 12 upon which the telephone lineterminates. The telephone line 13, 14: 1s lllustrated as extending tofour substations, M, J, R and W, each of which is provided with theusual substation equipment, which may comprise a telephone transmitterand receiver, an induction coil, a condenser and a switch hook forcontrolling the circuit. In addition, there is at each substation a bellwhich is bridged, through the condenser, from one side or the other ofthe telephone line to ground. The bells at substations M and J arebridged to ground from the conductor 13, and those at stations R and ifrom conductor 14: of the telephone line.

Only the calling end of the connecting circuit E is illustrated. Theother end of the connecting circuit may be assumed to extend toapparatus suitable for making connection with a calling line and "forcontrolling such connection. the circuit between the answering andcalling ends of the connecting circuit having included in it a repeatingcoil 10 with a bridged battery 15, in the usual way.

The talking eoiuluctors 1.6 and 17 of the conn cting circuit terminateupon the tip and ring contact surfaces, respectively, of the callingplug 11. The sleeve contact surface of the plug is the terminal of aconductor 18, which extends from the free pole of the battery 15 andincludes the windings of two relays 19 and 20. When the plug 11 isinserted in a spring jack 12, the circuit of this conductor 18 iscompleted to ground by way of the winding of the cut oit relay 21, thusbringing about the energization of the relays 19, 20 and 21. The relay21 has the usual function of disconnecting from the line, during itsuse, the branches that lead to the usual line signal apparatus (notshown). Relay 19 in operating, disconnects the tip of the plug from theoperators busy test circuit (not shown) and connects it with the talkingconductor 16. The relay 20 in operating, closes a circuit 501' the Howof current through the calling super visory lamp 22, subject to thecontrol of contacts 114 closed in position 17 ot' a calling cordsequence switch that will be referred to hereinafter. After the circuitof the calling lamp is closed by the actuation of the relay 20, when thecalling plug is inserted in the spring jack, the illumination of thelamp is under the control. of the called subscriber in the usual waythrough the medium of the calling supervisory relay 2 1, the shunt ofthe lamp controlled by this relay being also under the control ofcontacts 112 closed in position 17 of the calling cord sequence switch.

The calling cord sequence switch 100 may be similar to that illustratedin Patent #1,127,S08 to J. N. Reynolds and C. F. Baldwin, dated February0, 1915, or of any other suitable type. The sequence switch 100 controlssequence switch contacts 101 to 114, inclusive. Contact 101 of thesequence switch is arranged to close the local circuit "for the sequenceswitch operating ma gnct in all positions of the switch except thoseindicated by the figures adjacent to contact 101. This provides thattheswitch may Stop only in the positions indicated. The other sequenceswitch contacts 102 to 114C inclusive, are closed only in the positionsindicated by the figures adjacent to the respective contacts.

The positions of the calling cord sequence switches are as follows:

Ringing current is supplied to the connecting circuit by way of aconductor 25,

which has branche 20 and 27 at one end that are adapted under certainconditions to be completed to the tip and ring conductors. respectively,of the calling plug 11, and branches 28 and 29 at the other end whichare adapted under certain conditions to be completed to sources of twodifferent sorts of ringing current. In the present instance, the ringinggenerator 30 has associated with it three commutators 31, and Thecommutator 31 is adapted, during each cycle of its rotation, to connectthe conductor 29 for an interval with generator 30, and during thebalance of the cycle connect it with the free pole of battery 15.Commutator 32 is adapted, during each cycle of its rotation, toconnectthe conductor 28 twice with the ringing enerator 30 and twicewith the free pole of the battery 15 alternately. The arran ement issuch that when the branch, by way of the conductor 29, is connected withthe cord circuit, a single long impulse of ringing current is applied toone or the other side of the line, depending upon which of the branches20 and 27 is closed at the time; while. when the branch 28 is connectedwith the cord circuit, two short ringing impulses are applied. to oneside or the other of the line. with a relatively long interval ofsilence between each group of two short rings. The pick-up commutator 33rotates with the commutators 31 and and is arranged to send one impulseof current per rotation from the battery 15 out over the circuit in amanner hereinafter to be described, "tor the purpose ol marking thecycles of rotation of the commutators.

The organization described abovc provides ringing current for aplurality of the connecting circuits. and is one'ot' those that may beemployed for producing ditterent sorts of ringing current for theselective or distinctivc ringing of bclls at the various substations ofa party line. nmnhcr ol other methods of selectively or distinctivelyringing party line bclls are available in the art and may be employed,such as those which depend upon thc use of polarized pulsating currentsin conncction with polarizcd and biased bells. and those depending upondittercnt trcqucncv currents and so-called harmonic or tuned bclls, andit will be un lerstood that ringing generators and bells oi' tho th rorts may be substituted for those particularly disclosed herein, withoutdcparting from the spirit and scope of this invcntion.

The branch 20 of the conductor '25 has its connection with the tip sideof th connecting circuit controlled in sequence switch contacts l0l-5and l0--l8 \vhilc branch "2. has its connection with the ring side ofthe connecting circuit controlled in sequenciswitch contacts 10511 and105-13. The

connection between the other end of the con ductor 25 and the twobranches 2S and 2 over which the two sorts of ringing currents aresupplied from con'nnutators 32 and 'll. is controlled by sequence switchcontacts 100. branch 28 being connected with cinnluctm' 25 in positions100-5 and 100-ll, while branch 29 is eonncctedin positions 106-8 and100-13 of the switch contacts. That is, in position 5 of the sequenceswitch 100, source 30, 32 of ringing current is connected with the tipstrand of the connecting circuit; in position 8 of the sequence switch,source 30, 31 is connected with the tip strand, in position 11, source30, 32 is connected with the ring strand, and in position 13, source 30,31 is connected with the ring .strand of the connecting circuit.Contacts 1055, 105S, 104*11 and 1041'3 of the sequence switch operate toestablish a ground connection from one side o:t the connecting circuitwhen the other side of the circuit is connected to one or the other ofthe sources oi ringing current.

In the particular embodiment of the invention illustrated, the controlof the ringing current so as to ring any one 01": the four stations of aparty line is effected through the medium of four'selective keys M, J,R, and 1V, which are common to all of the connccting circuits of theoperators position. Other connecting circuits organized similarly to theone shown, are indicated by the taps which are represented as extendingfrom the conductors that lead to the common selective keys and theirassociated lamps m, j, r, and w. The selective keys M, J, R, and NV actthrough the medium of relays 38. 39 and 40, individual to eachconnecting circuit,'to determine which one of four branches 41, 42, 43,and 44 of a controlling circuit 45 shall have its circuit 'closed. Thesebranches 41, 42, 43 and 44 are brought successively into operativerelation with the controlling conductor 45 in the movement or thesequence switch 100 and through the medium of their respectiveassociated sequence switch contacts 1073 to 5, 1086 to S, 109-9 to 11,and 110-12 to 13. The completion of the controlling conductor 45throughtone or another of the branches 41, 42, 43 and 44 in the movementof the sequence switch acts through the medium of relay 36 included inthe controlling circuit to complete the circuit of the ringing conductorin the contacts 34 of that relay, and to control the stopping of thesequence switch in position to close the branches of the ringing circuitfor ringing the particular party line station that corresponds with theparticular selective key M, J, R, or V that has been depressed and theparticular branch 41, 42, 43 or 44 of the controlling circuit that hasbeen closed.

Assuming thatthe operator has received a call for station W of theparticular line that is illustrated in the drawing, and that the callhas come over the connecting C11- "cuit that is shown in the drawing.Under such circumstances the operator has her telephone set andcontrolling apparatus in connection with the particular cord circuitillustrated, and the switch contacts 202, 203, 204,

205, 207 and 208, which may be contacts as sociated with a listening keysequence switch, of which there would be one foreach connecting circuit,are-closed. The closure of these contacts, only one set of which may beclosed at a time, connects the selecting keys M, J, R, and 1V common tothe operators position with the particular connecting circuit thatis'tobe used in establishing the connection. This places the ringing controldevices of this particular connecting circuit under the control of thecommon selecting keys M, J, R and W'.

The arrangement of the ringing current controlling devices of eachconnecting circuit is such that normally the branch 44 of thecontrolling circuit 45 has its connection with earth completed by way ofthe back contacts 40, 47 and 48 of the relay 38, 39 and 40,respectively; and therefore, if the apparatus is in itsnormal'condition, itis not necessary for the operator to depress theselecting key lV. She inserts the calling plug 11 into the spring jack12. This act, through the agency of circuits and apparatus that need notbe particularlydescribed, completes the local circuit of the callingcord sequence switch operating magnet by way of sequence switch contact1021, and moves the sequence switch out of positlon .1 and into position\Vhen the operators telephone set and controlling apparatus isdlsconnected from the connecting cireuit,- which may result either fromthe operators listening out manually, or from a sequence switch that isassumed to control the switch contacts 202 to 208, inclusive, beingmoved as a result of the closure of the circuit due to inserting theplug 11 in the spring jack l2,the local circuit of the calling cordsequence switch is closed by way of sequence switch contacts 1032 tomove the sequence switch out of position 2.

As sequence switch 100 moves into position 3, it closes in sequenceswitch contacts 111. a path to ground for whichever of the branches 41,42, 43 and 44 may be closed in the relay contacts 46, 47 and 48. In theparticular case being described, as the relays 38, 39, and 40 are inert,it is the branch 44 that thus is given a ground connection As thesequence switch 100 moves into position 4, its further movement comesunder the control of the normal or resting contacts 35 of relay 36 byway of sequence switch contacts 103- 1 to 13. Therefore, beyond position4 the movement of the sequence switch 100 will continue only as long asrelay 36 remains inert. As sequence switch 100 moves l'rom position 3 toposition 11 inchisive, it brings the controlling conductor 45successively into communication with the branches 41., 42 and 43 by thesuccessive closure of the sequence switch contacts 107, 108 and 109. Butas each of these branches is open in its associated relay contacts,nothing happens.

\Yhen sequence switch 100 comes to position 12, it closes sequenceswitch contacts 110, and thus completes t path to ground for controllingconductor 45 by way of branch l-t, the resting contacts 18, 47 and 46 ofrelays '10, 39 and 38 respectively, and sequence switch contacts 111.This atlords a path for current tlow through relay 36, and theconsequent energization of that relay opens its back contacts 35 andinterrupts in these contacts the local energizing circuit ot' thesequence switch 100 by way of contacts 1(3, thus causing the sequenceswitch to come to rest in position 13 upon the opening of thealternative energizing path that. it has in position 12 by way ofsequence switch contact 101. in position 13 of the sequence switch 100ringing current from the' source 30. 31 is supplied to the line to ringthe bell at station \V', the path of flow being fron'i ringing generator30 through connnutator ll branch 2 sequence switch contacts IMP-13,winding of relay 49, contacts 3-1 oti relay 3t), conductor 25, branch27, sequence switch contacts 105-13, registering ring contact surfacesof plug 11 and spring jack 12, line conductor 14, through the.condensers and bells at stations R. and ll" to ground. The subscriber atstation it does not respond, because his signal is two short ringsinstead of the one long ring per cycle that is being given.

When the subscriber at station \V takes his receiver from the hook, therelay 10 included in the ringing circuit in energized and opens itscontact 30. The relay 19 is so constructed and adjusted as to beunresponsive to the current that flows through it during the ringiiig ofthe called station, but to respond when the called subscriber takes histelephone from the book. The opening of the contact 50 ot' the relay 49,on the response of the called subscriber, opens the short-circuit thathas hitherto existed around the winding of relay 51, thus permitting thecurrent flowing in the controlling conduc or 15 to pass through andenergize relay 51. When this relay operates, it introduces, in itscontacts another break in the above mentioned short-circuit to insurethe continued energization o't' relay 51 after relay 40 becomes inert.and also in its contacts 3:, closes a path to battery through arelatively low resistance coil 5-1 in shunt. ot' the winding of therelay 36 to' bring about the dei nerigization of the lastv mentionedrelay.

When relay I36 becon'ies inert, it permits the closure of its backcontact 35, thus again closing the local energizing circuit of thesequence switch 100 by way of sequence switch contacts 103-1bl Thereforethe sequence switch moves out of position 13 and continues itsn'iovement to position 16, where it is stopped by the opening of itsenergizing circuit in contacts of its 101 cam. In position 16 ot thesequence switch, the sequence switch contacts 101 and 105 are closed toconnect the tip and ring of the plug 11 with the conductors 16 and 17respectively of the connecting circuit, the plug having beendisconnected from its ringing current connections when the sequenceswitch moved out of position 13. As the called subscriber has histelephone off its hook, supervisory relay 2+ is energized and closes thelocal circuit of sequence switch 100 by way of sequence switch contacts10216. This causes the sequence switch to move to position 17, which isthe talking position.

\Vhile the conversation is proceeding and the called subscriber has hisreceiver oti its hook, supervisory relay :24 keeps the shunt of thecalling supervisory lamp 22 closed by way of sequence switch contacts112-1T. When the called subscriber replaces his receiver. relay 24becomes inert. and permits lamp :2 to light. The operator in taking downthe connection brings about the closure of the local energizing circuitof sequence switch 100 by way of contacts 10217, and the sequence switchin consequence moves to position 1, thus restoring the circuits to theirnormal condition.

The operation described above was under the assumption that it wasstation 1 that was to be signaled. If it is station R that i to becalled, the operator presses key it of her common selecting keys M, R,J, and "\V, while li tening in on this particular connecting circuit. Inthis condition the switch contacts 202, 203, 201, 205, 201' and 208 areclosed and the circuits of the common select-. ing keys are connectedwith this cord circuit. Pressing the selecting key R energizes relay 40over the path by way of contacts 201. contacts 59 of key R and restingcontgtcts 5S and 56 of keys J and M, respectively, tOiQjl'OlliKl. Uponthe release of selecting key 1%, after a momentary depression, a holdingcircuit is closed for relay 40 by way 0t. t'ront contact 63 of thatrelay, resting contacts 61 and 65 of relays 39 and 38 respectively.contacts 207 closed while the operator is in on this circuit, andresting contacts 62, 60, 5S and 56 of the selecting keys to ground.Relay -10, thus held energized, completes the circuit ot branch 43 toground by way of the front contact 48 of relay +10 and the restingcontacts i7, -16 of relays 39 and 38 respectively, and sequence switchcontacts 111 in positions 3 to 13 of the sequence switch.

The consequence of this is that when sequence switch 100, in movingbeyond position 41, reaches position 9 and closes switch contacts 109associated with the grounded bra ch 43, an energizing circuit for relay36 completed, which causes that relay to open its resting contact 35,thus breaking the local energizing circuit of the sequence switch closedin switch contacts 102- and bringing the switch to rest in position 10.

As the ringing code employed in this system depends upon one or morerings having a certain relation to each other, it is desirable that theapplication of ringing current to the circuit occur only at a particularpointin the ringing cycle. To accomplish this the arrangement is suchthat the sequence switch is brought to rest at a position one pointbefore that at which the particular ringing current selected is to beapplied, and is moved from this waiting t the ringing position by apickup impulse produced at the beginning of each ringing cycle by thecommutator 33. This action is eiiected through the medium of the relay37. When the to lay 36 is energized, the circuit of the relay 37 iscompleted to ground by way of the front contacts of relay 36. Theconnection of relay 37 with the battery is completed once for eachringing cycle by means of the pick-up commutator 33. Therefore, at thestart of the first ringing cycle after relay 36 has closed its contacts35, the relay 37 receives current for its energization by way of thepick-up commutator 33; and in' oper-' ating its contacts (36, relay 37disconnects its winding from the pick-up commutator and connects itdirectly to battery, so that thereafter the relay 37 remains energizedas long as its circuit is completed in the contacts 35 of relay 36.lVhen the first pick-up impulse, after relay 36 was operated, energizesrelay 37, that relay closes in its contact 67 an energizing circuit forsequence switch 100 by way of sequence switch contacts 103 in positions4, 7 or 10, these three positions being those in which the sequenceswitch waits upon the receipt of a pick-up impulse before it moves tothe immediately succeeding position where the selected ringing currentis applied.

The present assumption is that by reason of the depression of the key Rhaving brought about the closureot the branch 43, the sequence switch100 has been stopped in position 10, where it is awaiting the nextpick-u p impulse. Upon receipt of the pickup impulse, the relay 3?closes its contact (57, and the sequence switch is moved from position10 to position 11. In position 11, sequence switch contacts 106 areclosed to direct ringing current from source 30, 32 to ringing conductor25, and sequence switch contacts 105 are closed to connect the ringingcurrent thus applied to conductor 25 with the ring side of theconnecting circuit, and thence by way of conductor 14 of the linecircuit to stations R and N". The bells at both stations ring, and thesubscriber at station R, whose ringing code signal is being given,answers. The taking'of the receiver from its hook at station it bringsabout the energization of relays i9 and 51 and the deenergization ofrelay 3V in the same manner as was described in connection with theringing of station l \Vhen relay 3G is deencrgized. it closes in itsresting contacts 35 the local energizing circuit of the sequence switch100 by way of sequence switch contacts 1t)34 to 13, thus causing thesequence switch to HIOVO continuously from position 11, through position13, whence the movement is continued by way of sequence switch contacts101 to position'lfi, out of which position it'is moved in the mannerdescribed in connect ion with the ringing of station W V. If it isassumed to be station J that is to be signaled. the operator, Whilehavingher t'onnnon selecting keys M, J, R and W as. soclated with thisparticular connectlng ciring contact 65 of relay 38, contacts 207 closedwhile the operator inon this..circuit, and the resting contacts 62, 60,58 and 56 of the tour selecting keys, to ground. As a result, branch 42of the controlling circuit is complei ed to ground by way of thefrontcontact 47 ot' relays 3f). resting contact d6 of relay 3S andcontacts 1l13 to 13 0t tne sequence witch, while the other branches 41,43 and H- rcniain open. Consequently, when sequence switch 100 reachesposition (3 and closes sequence switch contacts 108 with which branch 42is associated, relay 36 opens its contact to stop the sequence switclrinthe next open position 7 of the controlling contacts 101, and'itscontacts 34: to close the ringing conductor in readiness for theapplication of ringing current to the circuit. Relay 3G, in closing itsfront contact 35, also places relay 37 in'reaiiiness to be operated uponthe occurrence cf the next pick-up impulse, this operation of relay 37acting, by the closure of its contact 67, to close the local energizingcircuit; of the sequence switch 100 by way of sequence switch contacts103-7, thus moving the sequence switch into position 8'. 1

, In position 8 of the sequence switch, contacts 106 of theswitchconnect ringing current from commutator 31 with ringing conductor 25,and contacts 1040f the switch connect conductor 25 with the tip side ofthe circuit and thence, by way of line conductor 7 13, ringing currentflows through the bells at stations M and J. As the current that isbeing applied is such as to give the code signal to which station Jresponds, the subscriber at that station takes his receiver from itshook. Thereafter the operation is as has been described in connectionwith the ringing of stations W and R, the taking of the receiverbringing about the deenergization of relay 36 to disconnect the ringingcurrent and move the sequence switch from the position 8, in which ithas been resting, through position 13, and thence to the talkingposition 17.

When it is station M that is to be signaled, the operator momentarilydepresses the common selecting key M wlnle listening in on theconnecting circuit that is to be used. This causes the initialenergization of relay 38 by way of switch contacts 202 and contacts 55of the selecting key M, and the continued energization of relay 38,after the key M is released, by way of switch contacts 207 and contacts62, 60, 58 and 56 of the four selecting keys in series. This closesbranch 11 to ground in the front contacts 10 of relay the other threebranches l2, l3 and 4st being left open. In this case, therefore, relayis energized as soon as the sequence switch 100 reaches position 3, inwhich it closes its contact 107 associated with branch 41-. and thesequence switch comes to rest in the next open position 1. Here itawaits the next pick-up impulse, which operates through relay 37 toclose the local energizing circuit of the sequence switch by way ofcontacts 103st and move the sequence switch into position 5. In positionsequence switch contacts 106 connect ringing current from the commutator32 with conductor 25. and sequence switch contacts lUl connect theringing current thus applied to conductor 25 with the tip side. of theconnecting circuit, and thence by way ol line conductor I to the bellsat stations M and J. Under these conditions the bells ring the codesignal of station M", and the subscriber at that station responds. Thetaking of the receiver from its book at. the called station acts, in themanner already described. to del nergize relay 36. thus disconnectingringing current 'lrom the line and closing the local energizing circuitol sequence switch 100 to move that switch out. of position 7). in whichit has been resting, through position 125, and eventually into thetalking position 17, as has already been described.

In each rase relay 51, locked up as a result of the response of thecalled subscriber, is released, upon the resumed movement of thesequence switch, by the breaking of its circuit in whichever of thesequence switch contacts 107, 108, 100 or 110 had its branch closed toeffect the signaling of the corresponding station.

When the operators common selecting keys M, J R and .V have been broughtinto association with any one of the connecting circuits, and have beenmanipulated to set the apparatus associated with that circuit for theapplication of a particular sort of ringing current to the line, thatsetting of the connecting circuit apparatus is maintained until theconnection is taken down or until the operator brings about a differentsetting of the cord circuit apparatus by pressing some other selectingkey while listening in on this circuit. This, in the particularembodiment of the invention illustrated, is accomplished by the mannerin which the holding or maintaining circuits for the setting relays 38,39 and 10 of the connecting circuit are made subject to the control ofswitch contacts associated with the selecting keys, the operatorscontrolling circuits and the connecting cord circuit itself. The commonholding or maintaining circuit for the relays 88, 39 and 40 has twobranch paths to ground. one of these branches being' closed in the.switch contacts 207, while the operator is listening in on theconnecting circuit. and the other being closed in contacts 206 while theoperator has her telephone and controlling apparatus disconnected fromthe connecting circuit. The contacts zoo and 207 are so arranged thatone of them is always closed before the other is opened, so that one orthe other of the branches of the holding circuit is closed at this pointat all times. of the contacts 'illli extends to earth by 'ay of contacts113 closed in positions 15} to 17-}; of the sequence switch lltt). whilethe branch completed in the contacts 207 extends to ground by way of thenormal or resting contacts (32. (30, 58 and so in series ol theselecting keys \V, R, .l and M.

As a result. after any one of the relays 3h. 2}!) and ll) has beenoperated by the depression ol' the corresponding selecting key, it isheld operated by one or the other of the ln'nlltllts ol the holdingcircuit as the operator listens in or listens out on the circuit. Whenthe connection is taken down. it being assumed that the operator is notin on the circuit at the lime and that the contacts 206 are. thereforeclosed. the relay 23S, 39 or stO that has been operated is released bythe opening ol the holding circuit in the sequence snitch contacts 113as the sequence switch [00 returns to its normal position l. Thesequence switch llltl is moved out of position 17 and into position 18upon the de ucrgization of relay ltt resulting from the removal of plugll from the jack [2. The driving circuit may be traced from ground,through the armature and back contact of relay 19, the sequence switchcontact 102, positions 2 to 17, and the power magnet of sequence switch100 to grounded battery. It the operator desired to change the setlhebranch by way ting of the connecting circuit in order to bring about theapplication of a different sort of ringing current to the called line,she listens in on the circuit, and then may withdraw the calling plug11, press the particular one of the selecting keys M, J, R and Wcorresponding with the desired setting, and reinscrt the plug; whereuponthe sequence switch lOO, which was returned to its normal position bythe withdrawal of the plug, is moved to the position determined by thenew setting of the selecting keys.

in the operators listening-in position, the closure of switch 'contacts207 places the holding circuit for the relays 38, 39 and i0 under thecontrol of the series of normally closed contacts (32, (50, 58 and 56 ofthe four selecting keys. Consequently, the depression of any one ofthese keys releases whichever of the relays 38, 39 and 40 is locked upby opening the corresponding set of holding contacts (32, G0, 58 or 56.The accompany ing closure of the contacts 55, 57 or 59 closes thecircuit for the energization of the corresponding relay 38, 39 or L0,depending upon the new setting desired, and the release of the selectingkey M, J or R closes the common holding circuit for the operated relayby way of the contacts 56, 58 or 60 before it opens the individualoperating circuit of the relay by way of the contacts 57 or 59. As thesetting corresponding with the selecting key W is the normal setting orthe connecting circuit, that key when depressed op rates merely torestore the normal setting by releasing any one of the relays 38, 39 and40 that may be held up through the common holding circuit.

In order that the operator may know the ringing current for which aconnecting circuit is set, each of the selecting keys M, d,

it and d has associated with it a lamp, '/)L,

j, r and 10, respectively, and the circuit ar rangement is such thatwhen the operator listens in on a connecting circuit. the lamps.corresponding with the sort oi ringing current for which the circuit isset. lights. This is accomplished bv connecting the lamps m, j. 7', andto with the circuits which extend from their mirres 'mnding keys to theswitch contacts 202, 203. 304;, and 305, and providing the lamps with acommon connection to battery by way 0 5 switch contacts 208 closed whenthe operator listens in on the circuit. If any one of the three relays38, 39 and 40 is up at the time the contacts 202, 203, 20% and 205 areclosed by the operator going in on the connection, a path to ground forthe circuit including the corresponding lamp m, y', or r is closed byway of the front contact 63, 64 or 65 of,

none of the relays are up when the operator listens in. and the settingconsequently is the normal setting for the ringing of station W, thepath for the flow of current to lamp to is completed by way of theresting contacts 63, (it and (35 ot' the three relays, contacts 207, andthe resting contacts of the tour selecting keys in series.

hat is claimed is:

1. The combination with a telephone connecting circuit, of a ringingcircuit having a plurality of branches a controlling circuit having acorresponding number of branches with a key in each branch for closingthe same, and an automatic switch adapted in its movement successivelyto establish the branches of said ringing circuit and simultaneouslybring itself under the control of the con-responding branch of saidcontrolling circuit.

2. In a telephone system. the combination with a plurality of connectingcircuits, of a plurality of electromagnetic ringing control switches foreach connecting circuit, operatorsmean's common to said connecting 'cirunits for selectively operating the electromagnetic ringing controlswitches of any one of the connecting circuits, and signals as-'sociated with said operators means, said signals being selectivelycontrolled'by the electromagnetic switches of an associated connectingcircuit.

3. in a telephone system, the combination with a plurality of connectingcircuits each ln ving a. plurality of ringing control switchesassociated therewith, of operators indicating means common to saidconnecting circuits. said iiulicating means being selectively responsiveto said ringing control switches to. indicate which one of said switchesis operated. and means for bringing said indicating means into operativere lation with any of said connecting circuits.

--l-. In a telephone system, the combination with telephone lines, of aconnecting circuit for establishing connection therewith, a switchclosed while the connection is established, means for supplying ringingcurrent of different characteristics, switching mechanism i'orselectively controlling the application of ringing current of saiddifferent characteristics to said connecting circuit, selecting keys forsetting said switching mechanism to appplv current of one sort oranother, and holding means for maintaining the setting of said switchingmechanism, said holding means being under the alternative control ofsaid first mentioned 1 switch and said selecting keys.

5. in a telephone system. the combination with a connecting circuit. inans for supplying ringing current of diti'erent characteristics,switching mechanism for applying ringing current of said differentcharacteristics to said connecting circuit, a plurality ofelectromagnetic switches for selectively controlling said switchingmechanism, a' selecting key associated with each of said electromagneticswitches, an energizing circuit for each electromagnetic switch adaptedto be completed by the associated key, and locking circuits for saidelectromagnetic switches having a common branch controlled in contactsof each of said keys.

6. In a telephone system, the combination with a connecting circuit, ofa ringing circuit having a plurality of branches, a controlling circuithaving a corresponding number of branches, a locking relay for each ofsaid controlling circuit branches adapted when operated to close theassociated branch, a selecting key for controlling the operation of eachlocking relay, and an automatic switch adapted in its movementsuccessively to establish the branches ofsaid ringing circuit and comeunder the control of the corresponding branch of said controllingcircuit.

7. In a telephone system. the combination with a connecting circuit, ofa ringing circuit having a plurality of branches, a controlling circuithaving corresponding branches, a selecting key for each branch circuitadapted when operated to change the electrical condition of theassociated branch, an automatic switch adapted in its movementsuccessively to establish the branches of said ringing circuit and comeunder the control of the corresponding branch of said controlling circuit, and means I'ESPOl'lSlVG to the changed electricalcondition of anyone of said coir trolling branches for stopping said automatic switch.

8. In a telephone system, the combination with a connecting circuit, ofa rihgii'ig circuit, having a plurality of branches, a controllingcircuit having corresponding b 'anches, means for changing theelectrical condition of any'ot' said controlling circuit branches, anautomaticswitch adapted in its movement. successively to establish thebranches of said ringing circuit, an electromagnetic stopping device Forsaid switch responsive to the changed electrical condition of any ofsaid controlling circuit branches, and means for bringing said stoppingdevice into eom'iection with said controlling circuit branchessimultaneously with the establishing of the corresponding ringingcircuit branches.

9. In a telephone system, the combination with a connecting circuit, ofa normally open ringing circuit having a pluralitiy of normally openbranches, a controlling circuit having a corresponding number ofbranches, means for altering the electrical condition of any one of saidcontrolling circuit branches, an automatic switch adapted in its of saidcontrolling movement successively to close the branches of said ringingcircuit and simultaneously bring itself under the control of thecorresponding branches of said controlling circuit, and means responsiveto the changed electrical condition of any one of said controllingcircuit branches for stopping said switch and closing said ringingcircuit.

10. In a telephone system, the combination with a connecting circuit, ofa normally open ringing circuit having a plurality of normally openbranches, an automatic switch adapted in its movement successively toclose said branches, means for closing said ringing circuit and stoppingsaid switch at a waiting point immediately preceding a branchclosingposition of the switch, and means for moving said switch from saidwaiting point to said n'anch-closing point.

11. In a telephone system, the combinzv tion with a connecting circuit,of a normally open ringing circuit having a plurality of normally openbranches. an automatic switch adapted in its movement to close saidbranches successively, switching mechanism for closing said ringingcircuit and simultaneously stopping said switch at a waiting pointimmediately preceding a branch-clos ing position. a. source of pi k-upimpulses. means responsive to a pick-up impulse 'l'or moving saidautomatic switch from a waiting point to the correspondinglJl'illltJlht'lUS- ing point. and a switch closed by said switchlugnu-chanism for rendering said means operative. I

12. In a telephone system, the combination with a party line. ol aconnecting circuit, a ringing circuit therefor having a plurality ofbranches. sources ol di llcrenl sorts of cur rent in said branchesadapted for distinctively signaling the stations ol said partv line, acontrolling circuit having branches corresponding with aid ringingcircuit branches. means l'or changing the electrical conditions ol anyone of said cont-rolling circuit branches, an automatic switch adaptedin its movement to establish successively the branches of said ringingcircuit and bring ilscll. under the control of correspoiuling branchesol the controlling circuit. means responsive to the changed electricalcondi tion oi any controlling briinch for stopping said switch to applya particular sort of ringing current to the line, and means operated bythe response ol the called subscriber for moving said automatic switchto disconnect. the ringing current and establish the talking conditionol said circuit.

13. A telephone ringing circuit having a plurality of branches, anautomatic switch adapted in its movement to establish said branches insuccession, means for stopping said switch when a particular branch hasbeen established, and means controlled by

